Helper functions: Perl language

use warnings;
use strict;
use POSIX qw(strftime);  # current time

sub logger {
    my $subname = (caller(0))[3];
    my ($package, $filename, $line) = caller();
    my ($msg, $level, $modname) = @_;
    my $message;
    $modname = $subname unless $modname;
    my $current_date = strftime("%Y-%m-%d %H:%M:%S", localtime);
    $message = "] $current_date ${filename} ${modname} ${line} | $msg";
    if ($level eq 1) {
        print("$message\n");
    } elsif ($level eq 2) {
        print(STDERR "$message\n");
    } elsif ($level eq 3) {
        print(STDERR "$message\n");
        exit $line;
    }
}

unless (-d $path) {
    logger("$path: No such file or directory", 3, $subname);
}

use Cwd 'abs_path';  # get absolute path

sub finder {
    my $subname = (caller(0))[3];
    my ($opts) = @_; # hashref
    $opts ||= {};
    my $path     = $opts->{path}    // '.';
    my $type     = $opts->{type}    // '';
    my $pattern  = $opts->{pattern} // '';
    my $hidden   = $opts->{hidden}  // 0;
    unless (-d $path) {
        logger("$path: No such file or directory", 3, $subname);
    }
    $path =~ s,/$,,;  # remove trailing /
    my @directories;
    opendir (my $dir, $path);
    while (my $entry = readdir $dir) {
        my $full_path;
        if ($path =~ /^\//) {  # double check for full name vs relative name
            $full_path = $path."/".$entry;
        } else {
            $full_path = abs_path($entry);
        }
        unless ($hidden) {
            next if $entry =~ /^\./;  # show hidden files or don't
        }
        next if $entry eq '.' or $entry eq '..';  # ignore . and .. directory
        if ($type eq "d") {
            next unless -d $full_path;
        } elsif ($type eq "f") {
            next unless -f $full_path;
        } elsif ($type eq "l") {
            next unless -l $full_path;
        } else {
            next unless -e $full_path;
        }
        if ($pattern) {
            if ($entry =~ /$pattern/) {
                push(@directories, $full_path);
            }
        } else {
            push(@directories, $full_path);
        }
    }
    return sort @directories;
    closedir $dir;
}

my @root = finder({path => "/tmp", type => "d", pattern => "systemd"});
foreach my $dir (@root) {
    print("$dir\n");
}

use File::Path qw(make_path);  # directory handler
use File::Fetch;  # remote handler
use File::Basename;  # filename handling

sub fetcher {
    my $subname = (caller(0))[3];
    my ($opts) = @_;  # hashref
    $opts ||= {};
    my $url        = $opts->{url}       // '';
    my $name       = $opts->{name}      // '';
    my $directory  = $opts->{directory} // $ENV{PWD};  # fallback to PWD
    make_path($directory) unless -d $directory;  # create output directory
    my $ff = File::Fetch->new(uri => $url);
    my $file = basename($url);
    my $full_name = $directory.'/'.$ff->file;
    my $return_value = {
        name => $name,
        url => $url,
        file => $ff->file,
        full_name => $full_name,
    };
    if (-f $full_name) {
        print(STDERR "[ignore] file already exists ");
        return $return_value;
    }
    # fetch
    my $where = $ff->fetch(to => "$directory/$name") or logger($ff->error, 3);
    return $return_value;
}

fetcher({
    url => "https://musl.libc.org/releases/musl-1.2.5.tar.gz",
    name => "musl.tar.gz",
    directory => "/tmp/fetch"
});

ls -lhtr /tmp/fetch

fetcher({
    url => "https://musl.libc.org/releases=musl-1.2.5.tar.gz",  # invalid URL
    name => "musl.tar.gz",
    directory => "/tmp/fetch"
});

sub command {
    my $program = $_[0];
    my $path = $ENV{"PATH"};
    my @directories = split(":", $path);
    my $found = '';
    foreach my $dir (@directories) {
        my $full_path = "$dir/$program";
        if (-x $full_path) {
            $found = $full_path;
            last;
        }
    }
    return $found;
}

if (command("magick")) {
    $found_im = 0;
    $runner = command("magick");
} else {
    $found_im = 1;
}

sub commander {
    my $subname = (caller(0))[3];
    my ($package, $filename, $line) = caller();
    my @commands = @_;
    my $msg = "] $subname $line @commands";
    my $_command = "@commands";
    my $_cmd_output = `$_command`;
    my $err_msg = $!;
    my $cmd_exit_code = $? >> 8;
    chomp($_cmd_output);
    my @cmd_output = split("\n", $_cmd_output);
    print(STDERR "$msg: error") if $cmd_exit_code;
    if ($err_msg) {
        print(": $err_msg\n");
    } else {
        print("\n");
    }
    return (\@cmd_output, $cmd_exit_code);
}

my ($ref_cmd_output, $exit_code) = commander("ls -l /tmp");
exit 1 if $cmd_exit_code;  # exit on error
my @cmd_output = @{$ref_cmd_output};
foreach my $line (@cmd_output) {
    print("$line\n");  # do whatever you want with it
}