...I need to make an output file with the first letter of the first name, last 3 letters of last name...

use strict;
use warnings;

my $firstName = 'PATRICK';
my $lastName  = 'STERL';

my $fileNamePart = "$firstName$lastName" =~ s/^(.).+(...)$/\L$1$2/r;

warn qq{Be careful: "$fileNamePart" may be an obscene word.};
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