Acts in the very same way as perl substitution operation
STRING =~ s/REGEXP/REPLACEMENT/OPTIONS,
returning the resulting string.
Searches a string for a pattern, and if found,
replaces that pattern with the replacement text.
If the REPLACEMENT string
contains a $ that looks like a variable,
the variable will be interpolated
into the
REPLACEMENT at run-time.
Options are:
e - evaluate REPLACEMENT
as a Perl expression,
g - replace globally, i.e., all occurrences,
i - do case-insensitive pattern matching,
m - treat string as multiple lines,
that is, change ^
and $ from matching the start or end
of the string to matching the start or end of any line anywhere
within the string,
s - treat string as single line,
that is, change .
to match any character whatsoever, even a newline, which
normally it would not match,
x - use extended regular expressions.