Shell Programming and Scripting

my $str="This is a testing string";
print $1 if $str=~/This.*(test)?.*$/;

print $1 if $str=~/This.*(test).*$/;

Problem:-
You have a pattern with a greedy quantifier like *, +, ?, or {}, and you want to stop it from being greedy.
A classic case of this is the naïve substitution to remove tags from HTML. Although it looks appealing,
s#<TT>.*</TT>##gsi, actually deletes everything from the first open TT tag through the last closing one
This would turn "Even <TT>vi</TT> can edit <TT>troff</TT> effectively." into "Even
effectively", completely changing the meaning of the sentence!

Solution
Replace the offending greedy quantifier with the corresponding non-greedy version. That is, change *, +, ?,
and {} into *?, +?, ??, and {}?, respectively.

perl -wle '
$str="This is a testing string";
print $1 if $str=~/This.*?(test).*$/;
' infile.txt

By Tom Christiansen & Nathan Torkington; ISBN 1-56592-243-3, 794 pages.
First Edition, August 1998.

my @arr=("This is a testing string","This is a tesing string");
map {print $1,"\n" if /This.*?(test)?.*$/} @arr;
print "--\n";

test (here there do have test, so have to force math)
(here no match, so just nothing)
--