Path: utzoo!attcan!uunet!samsung!brutus.cs.uiuc.edu!jarthur!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: Command substitution or Common novice bug
Message-ID: <7566@jpl-devvax.JPL.NASA.GOV>
Date: 27 Mar 90 19:13:33 GMT
References: <1460@kuling.UUCP>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 29

In article <1460@kuling.UUCP> jand@kuling.UUCP (Jan Dj{rv) writes:
: Should command substitution work inside double quotes?
: It sure doesn't for me:
: 
: % perl -e 'print "`date` ", `date`, "\n";'
: `date` Tue Mar 27 10:50:02 METDST 1990
: 
: Is there any reason for this behaviour? As an seasoned shell programmer
: I often make this mistake. This is my most common novice bug (I never seem
: to learn...) and I'm sure others who program in shell make the same mistake.
: 
: Can't perl change in this respect (please).

Sorry.  Not only would it break already existing scripts, but I don't like
multiple-substitution-pass semantics.  It's part of what makes shells so
messy.  You'll note that it's already documented under TRAPS that

    The backtick operator does variable interpretation without regard to the
    presence of single quotes in the command.

This is another manifestation of the same thing.  Just because you get into
double quotes or backticks doesn't mean you're in a shell.  It only means
that you can interpolate variables and backslash sequences in the string
so delimited.

The fact that I've selected the features of Perl from many languages you like
implies that I've rejected some features from some of the languages you like.

Larry