Shell Programming and Scripting

cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("-8.90e10")?"Looks like a number.\n":"Not a number.\n")'
Looks like a number.
cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("89d")?"Looks like a number.\n":"Not a number.\n")'
Not a number.

#!/usr/bin/perl

print "Enter a term: ";
$Input = <STDIN>;
print "\n";

if ($input == [0-9]) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ($input =~ /^[0-9]+$/) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}

#!/usr/bin/perl
use strict;

print "Enter a number: ";
chomp (my $num = <STDIN>);

if ($num =~ m/^-?\d+$/) {
    print "An integer \n";
}
elsif ($num =~ m/^-?\d+[\/|\.]\d+$/) {
    print "real number! \n";
}
else {
    print "not a number \n";
}

#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ( $input =~ /^[\+-]*[0-9]*\.*[0-9]*$/ && $input !~ /^[\. ]*$/  ) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}