#!/usr/bin/perl -w
use strict;

my %validators = (
    'singleletter' => 'm/^[a-zA-Z]$/',
    'integer' => 'm/^\d+$/',
    'nottoolongstring' => 'length $_ < 10'
);

sub check
{
    my ( $type, $value ) = @_;
    my $v = $validators{$type};
    return 0 unless defined $v;
    $_ = $value;
    return eval $v ? 1 : 0;
}

print check( 'singleletter', 'a' ) . "\n";
print check( 'integer', 'a' ) . "\n";
print check( 'nottoolongstring', 'a' ) . "\n";