Not really a function. Returns the value of the last command in the
sequence of commands indicated by BLOCK. When modified by the while
or
until
loop modifier, executes the BLOCK once before testing the loop
condition. (On other statements the loop modifiers test the conditional
first.)
do BLOCK
does not count as a loop, so the loop control statements
next
, last
, or redo
cannot be used to leave or restart the block.
See perlsyn for alternative strategies.
This form of subroutine call is deprecated. See perlsub.
Uses the value of EXPR as a filename and executes the contents of the file as a Perl script.
- 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 directories, 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: