#!/usr/bin/perl

# does the argument contain anything that is not a digit?
# note null string counts as a digit...

sub is_number($) {
    my( $number ) = shift;

    if( $number =~ /\D/ ) {
        return 0;
    }
    else {
        return 1;
    }
}

print is_number( "aslkdjf" ); # prints 0
print is_number( "1/.,234" ); # prints 0
print is_number( "1234" );    # prints 1
print is_number( "" );        # prints 1