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B.25. Converting Other Languages to Perl
If you''ve got old sed and
awk
programs that you
wish were written in Perl, you''re in luck. Not only can Perl do
everything that those can do, there''s also a
conversion program available, and
it''s probably already installed on your system. Check the
documentation for s2p (for converting from
sed) or
a2p (for converting from
awk).[421] Since programs don''t write programs as
well as people do, the results won''t necessarily be the best
Perl -- but it''s a start, and it''s easy to tweak. The
translated program may be faster or slower than the original, too.
But after you''ve fixed up any gross inefficiencies in the
machine-written Perl code, it should be comparable.
[421]If you''re using
gawk or nawk or some other
variant, a2p may not be able to convert it. Both
of these conversion programs were written long ago and have had few
updates except when needed to keep working with new releases of
Perl.
Do you have C algorithms you want to use from Perl? Well,
you''ve still got some luck on your side; it''s not too
hard to put C code into a compiled module that can be used from Perl.
In fact, any language that compiles to make object code can generally
be used to make a module. See the perlxs
manpage, and the Inline module, as well as the
SWIG system.
Do you have a shell script that you want to convert to Perl? Your
luck just ran out. There''s no automatic way to convert shell to
Perl. That''s because the shell hardly does anything by itself;
it spends all of its time running other programs. Sure, we could make
a program that would mostly just call system for
each line of the shell, but that would be much slower than just
letting the shell do things in the first place. It really takes a
human-level of intelligence to see how the shell''s use of
cut, rm,
sed, awk, and
grep can be turned into efficient Perl code.
It''s better to rewrite the shell script from scratch.
