regex in Perl: the binding operator

• The binding operator: =~ (or its opposite !~)
• Looks like an assignment, but it's not
• Binds an expression (variable) to one of three regex operators:
  • Match: m//
  • Substitution: s///
  • Translation: tr/// or y///
• The binding operator is assumed against the "default" variable $_ when one of these operators is found by itself, and the match operator is assumed when // is used with the binding operator:

  	while( <> ) {		# Explicitly, while( $_ = <> )
  	    next if( /^#/ );	# Skip comments, or
  				# explicitly, next if( $_ =~ m/^#/ );
  	    print;
  	}