do EXPR Uses the value of EXPR as a filename and executes the contents
of the file as a Perl script. Its primary use is to include
subroutines from a Perl subroutine library.
do 'stat.pl';
is just like
eval `cat stat.pl`;
except that it's more efficient and concise, keeps track of the
current filename for error messages, searches the @INC
libraries, and updates %INC if the file is found. See
"Predefined Names" in perlvar for these variables. It also
differs in that code evaluated with "do FILENAME" cannot see
lexicals in the enclosing scope; "eval STRING" does. It's the
same, however, in that it does reparse the file every time you
call it, so you probably don't want to do this inside a loop.
If "do" cannot read the file, it returns undef and sets $! to
the error. If "do" can read the file but cannot compile it, it
returns undef and sets an error message in $@. If the file is
successfully compiled, "do" returns the value of the last
expression evaluated.
Note that inclusion of library modules is better done with the
"use" and "require" operators, which also do automatic error
checking and raise an exception if there's a problem.
You might like to use "do" to read in a program configuration
file. Manual error checking can be done this way:
# read in config files: system first, then user
for $file ("/share/prog/defaults.rc",
"$ENV{HOME}/.someprogrc")
{
unless ($return = do $file) {
warn "couldn't parse $file: $@" if $@;
warn "couldn't do $file: $!" unless defined $return;
warn "couldn't run $file" unless $return;
}
}
Just out of curiosity, why would the second attempt work? Are you modifying the file before retrying? Is it a configuration file or something?
In reply to Re: Failed require looks like it succeeded
by blahblahblah
in thread Failed require looks like it succeeded
by Anonymous Monk
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