#!/usr/bin/perl

use strict;
use warnings;

my $val = 101.24;
validate( 3, 2, $val );

sub validate {
    my $v1 = $_[0];
    my $v2 = $_[1];
    my $v3 = $_[2];
    print "Values are $v1 \t $v2 \t $v3 \n";

    if ( $v3 =~ m/^\d{$v1}\.\d{$v2}$/ ) {
        print "its a good one\n";
    }
    else {
        print "Not Good!!";
    }
}
[download]

I tidied the tidied.

my $val = 101.24;
print match_decimal_format( 3, 2, $val ) ? "Valid!\n" : "Invalid...\n"
+;

sub match_decimal_format {
    my ( $leading, $trailing, $number ) = @_;
    return $number =~ m/^ [0-9]{$leading} \. [0-9]{$trailing} $/x;
}
[download]