the regexp only needs to be compiled once
You gotta read the rest of the text right around there. I'd quote it, but I don't have my camel with me (I'm on a trip). But the
perlop manpage says:
PATTERN may contain variables, which will be interpolat
+ed (and
the pattern recompiled) every time the pattern search i
+s evalu-
ated, except for when the delimiter is a single quote.
+ (Note
that $(, $), and $| are not interpolated because they l
+ook like
end-of-string tests.) If you want such a pattern to be
+ com-
piled only once, add a "/o" after the trailing delimite
+r. This
avoids expensive run-time recompilations, and is useful
+ when
the value you are interpolating won't change over the l
+ife of
the script. However, mentioning "/o" constitutes a pro
+mise
that you won't change the variables in the pattern. If
+ you
change them, Perl won't even notice. See also
"qr/STRING/imosx".
Thus, /o is useful only when there are variables in the pattern. And you had no patterns with variables!