Checking if a Perl Value is a Number

Because Perl stores both numbers and strings in the same variable, it's often necessary to identify if a given variable contains a valid number. The following simple subroutine returns true if the value passed to it is numeric...

sub IsNumber
{
   my $String = $_[0];
   return $String =~ m/^-?([0-9]+\.)?[0-9]+$/;
}

It makes use of Perl's regular expression processing. There is a speed overhead in calling the regular expression parser but sometimes that's a cost worth bearing, as here, when the simplicity of the code outweighs the price in speed of execution.

This may be used directly in a test as...

if (IsNumber $MysteryVariable) {# do something... }

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