#!/usr/bin/env perl
use 5.034;
my $text = <<'EOT';
This is an appt: 1203
So is 1001.
But 8675 is not.
EOT
chomp($text);
my $digits_4_re = qr{ (? 1, 1203 => 1, );
sub _anchor_if_apt {
my $candidate = shift;
if ( exists $valid_appt_numbers{$candidate} ) {
return _anchor_for_num($candidate);
} else {
return $candidate;
}
}
sub _anchor_for_num {
my $unit = shift;
return qq{$unit};
}
$text =~ s{($digits_4_re)}{ _anchor_if_apt( $1 ) }xsmeg;
say $text;
exit 0;
__END__
$ perl texty.plx
This is an appt: 1203
So is 1001.
But 8675 is not.