You don't need an if statement because the expression
$_[0] =~ /^\s*\+\-?\d+\s*$/

[download]
is evaluated before the return.

In a scalar context it returns the number of matches.

Therefore as the regex is anchored start and end, if the supplied string is an integer the regex returns 1 otherwise 0, which are evaluated as true and false. Thus the above routine could be employed as follows 

if (is_integer_string($input){
   do_integer_function($input);
}
else{
   die "You must supply an integer\n";
}

[download]
You need to check if the modulus of the numbers is zero, perhaps a has_remainder function?

Hope that clarifies.

In reply to Re: finding multiples of two values by Utilitarian
in thread finding multiples of two values by urnumdei

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