Use the -M test operator. It returns the age of a file in days, so, for example, if you want to process only files from yesterday, the code could look like this: (untested)

foreach my $file (@filelist) {
    if ( int( -M $file ) < 1 ) {
        # do something with a file
    }
}
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int () is used because -M returns values like 0.50 when a file is less than a day old.

If you want to perform a specific task, please tell what you want to do with the files, I'll be glad to write some example code.

Update:

As Utilitarian was kind enough to suggest, readdir works just fine. However, I would try using File::Find, its both simple and powerful, in case you'll need some extra functionality later on. Here's an example of it's use: (this time it's tested ;] )

#!/usr/bin/perl -w
use strict;
use File::Find;

my $directory = "d:/usr";

print "List of files newer than yesterday in $directory:\n";

find(\&process, $directory);
sub process {
    if ((int(-M) < 1) && (-f)) {
        print "  $File::Find::name\n";
    }
}
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Output:

List of files newer than yesterday in d:/usr:
  d:/usr/newfile1.txt
  d:/usr/newfile2.txt
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The -f file test operator ensures we process only files, normally the output would contain d:/usr too. The process sub is executed for every file found in a directory, so feel free to modify it for your own needs.

Rgards,
Luke