if ($file) {
    ...
    open my $file, "< $file",
      or print &reasons();
    ...
        foreach my $file (@all_lines) {
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Why do you have three different variables named $file?

    while (<$file>) {
        my @all_lines = <$file>;
        foreach my $file (@all_lines) {
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When you enter the while loop the first line is read into the $_ variable and then the rest of the lines are read into the @all_lines variable. @all_lines does not contain all of the lines because the first line is missing.

It looks like you may want something like this:

my %systemcmd = (
    add       => sub { 'addqueue', '-h', $_[ 0 ], '-q', $_[ 0 ], '-i',
+ '3' },
    remove    => sub { 'removequeue', '-f', '-q', $_[ 0 ] },
    status    => sub { 'lpstat', "-p$_[0]" },
    cancel    => sub { 'cancel', '-e', $_[ 0 ] },
    add_slurp => sub { 'addqueue', '-h', $_[ 0 ], '-q', $_[ 0 ], '-i',
+ '3' },
    );


if ( $file ) {
    $file = lc $file;
    open my $FH, '<', $file or die reasons();
    print "Please wait... Reading from the file... \n";
    sleep 5;

    <$FH>;  # remove first line
    while ( my $line = <$FH> ) {
        if ( -e "/var/spool/lp/request/$line" ) {
            die "This printer is already defined!\n";
            }
        else {
            print "Adding queue \"$line\"\n";
            sleep 1;
            my @args = $systemcmd{ add_slurp }->( $line );
            0 == system @args or warn "system @args failed: $?";
            }
        }
    close $FH;
    exit 0;
    }
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