our $type;

BEGIN {
    $type ||= shift or die "no type";
}

##</code><code>##

#!/usr/bin/perl -an

our $type;

BEGIN {
    $type ||= shift or die "no type";
}

if ( $type eq 'letters' ) {
  print if $_ =~ /[[:alpha:]]/;
} elsif ( $type eq 'numbers' ) {
  print if $_ =~ /\d/;
} else {
  print "bad type: $type"
}