The following assumes that the input names are formatted correctly. (If not you might want to look at the lc and ucfirst functions.)

use strict;

my @fullnames = ("Smith, David", "Lamb, Mary", "Depp, Johnny", "Child,
+ Julia");

foreach my $fullname (@fullnames) {
    my ($last, $first) = map {s/^\s*//; $_} split /,/, $fullname;
    $first =~ s/^(\w).*/$1/;
    my $id = $first . $last;
    print "\$id = $id\n";
}
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