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From: PerlFAQ Server on 30 Mar 2010 18:00
This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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5.4: How can I use Perl's "-i" option from within a program?

"-i" sets the value of Perl's $^I variable, which in turn affects the
behavior of "<>"; see perlrun for more details. By modifying the
appropriate variables directly, you can get the same behavior within a
larger program. For example:

# ...
{
local($^I, @ARGV) = ('.orig', glob("*.c"));
while (<>) {
if ($. == 1) {
print "This line should appear at the top of each file\n";
}
s/\b(p)earl\b/${1}erl/i; # Correct typos, preserving case
print;
close ARGV if eof; # Reset $.
}
}
# $^I and @ARGV return to their old values here

This block modifies all the ".c" files in the current directory, leaving
a backup of the original data from each file in a new ".c.orig" file.



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The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
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