spaces-to-tabs: Simple regex sample

spaces-to-tabs

#! /usr/bin/perl
#
# spaces-to-tabs-filter
#
# A simple regex example
#    perl -e 'while (<>) { $line = $_; $line =~ s/    /\t/g; print $line; }' < foo_spaces.py > foo_tabs.py
#


while (<>) {
    $line = $_; 

    # - Replace the string "    " (four spaces) with a tab character
    # - 'g' at the end means "Do this globally" -- ie, replace all occurrences.
    $line =~ s/    /\t/g; 

    # The / character is the traditional regex delimiter in Perl.  
    # Perl lets you use any character (?) for this,
    # which can be convenient to avoid escaping things.
    # These are equivalent:

    # Replace \ with / characters:
    # $line =~ s/\//\\/g;  # here we escape both / and \ characters
    # $line =~ s!\\!/!g;  # ... though we only have to escape \ chars.

    print $line;
}