Avoiding mistakes in perl

You can control perl's level of "strictness" using command line switches and pragmas

the -w switch

#!/usr/local/bin/perl -w

# deliberate_mistake.pl

$variable = 5; $varaible++;

print "new value = $variable\n";

>>>deliberate_mistake.pl
Name "main::varaible" used only once: possible typo at deliberate_mistake.pl line 5.
new value = 5

the strict pragma

This forces all variables to be explicitly declared using the my keyword.

#!/usr/local/bin/perl -w

# deliberate_mistake2.pl

use strict; # forces all variables to be declared

my $variable = 5; $varaible = $variable + 1;

print "new value = $variable\n";

Notice this would not get caught by the -w switch

>>> deliberate_mistake2.pl
Global symbol "$varaible" requires explicit package name at deliberate_mistake2.pl line 7.
Execution of lectures/1_intro/deliberate_mistake2.pl aborted due to compilation errors.