#!/usr/bin/perl --
use strict;
use warnings;
use POSIX qw/ strftime mktime /;
Main( @ARGV );
exit( 0 );
sub Main {
    ...    
    if( FileUpdatedToday( $filename ) ){
        print "\ file has already been updated today";
    } else {
        UpdateFile( $filename );
    }
    if( not -s $temp ){
        EmailReport( $temp );
    }
}
sub EmailReport {
    my( $temp ) = @_;
    exec $^X, $emailPL, or die "problem with $emailPL";
}
sub FileUpdatedToday {
    ...
    return !!1;
    ..
    return !!0;
}
sub UpdateFile {
    ...
}
##</code><code>##

sub TestFileUpdatedToday {
    require Test::More;
    Test::More->import( tests => 4 );
    PrepareTestfiles('testfiles');
    my $notexist = 'testfiles/notexist';
    my $empty    = 'testfiles/empty';
    my $stale    = 'testfiles/stale';
    my $updated  = 'testfiles/updated';
    for my $file ( $notexist , $empty, $stale ){
        ok( ! FileUpdatedToday( $file ), "FileUpdatedToday( $file ) should not be true");
    }
    ok( FileUpdatedToday( $updated ), "FileUpdatedToday( $updated ) should be true");
}