use strict;
print "enter a number: ";
my $num = <STDIN>;
if ($num !~/^[+-]?\d+\.?\d*$/){print "this is not a number\n"}
else {print "your number is $num\n"}


__OUTPUT__
34  -> your number is 34
34.56  -> your number is 34.56
-1 -> your number is -1
34gtf -> this is not a number