perlfunc gods <P> do - turn a <FONT SIZE=-1>BLOCK</FONT> into a <FONT SIZE=-1>TERM</FONT> <P> <HR> <P> do <FONT SIZE=-1>BLOCK</FONT> <P> do <CODE>SUBROUTINE(LIST)</CODE> <P> do <FONT SIZE=-1>EXPR</FONT> <P> <HR> <P> Not really a function. Returns the value of the last command in the sequence of commands indicated by <FONT SIZE=-1>BLOCK.</FONT> When modified by a loop modifier, executes the <FONT SIZE=-1>BLOCK</FONT> once before testing the loop condition. (On other statements the loop modifiers test the conditional first.) <P> <FONT SIZE=-1>A</FONT> deprecated form of subroutine call. See [perlman:perlsub|the perlsub manpage]. <P> Uses the value of <FONT SIZE=-1>EXPR</FONT> 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. <P> <PRE> do ''; </PRE> <P> is just like <P> <PRE> scalar eval `cat`; </PRE> <P> except that it's more efficient and concise, keeps track of the current filename for error messages, and searches all the <STRONG>-I</STRONG> libraries if the file isn't in the current directory (see also the <CODE>@INC</CODE> array in [%linkNodeTitle "perlman:perlvar|Predefined Names", $NODE, "Predefined Names",{anchor=>"Predefined_Names"};%]). It is also different in how code evaluated with <CODE>do FILENAME</CODE> doesn't see lexicals in the enclosing scope like <CODE>eval STRING</CODE> does. It's the same, however, in that it does reparse the file every time you call it, so you probably don't want to do this inside a loop. <P> If [perlfunc:do|do] cannot read the file, it returns undef and sets <CODE>$!</CODE> to the error. If [perlfunc:do|do] can read the file but cannot compile it, it returns undef and sets an error message in <CODE>$@</CODE>. If the file is successfully compiled, [perlfunc:do|do] returns the value of the last expression evaluated. <P> Note that inclusion of library modules is better done with the [perlfunc:use|use()] and [perlfunc:require|require()] operators, which also do automatic error checking and raise an exception if there's a problem. <P> You might like to use [perlfunc:do|do] to read in a program configuration file. Manual error checking can be done this way: <P> <PRE> # read in config files: system first, then user for $file (&quot;/share/prog/defaults.rc&quot;, &quot;$ENV{HOME}/.someprogrc&quot;) { unless ($return = do $file) { warn &quot;couldn't parse $file: $@&quot; if $@; warn &quot;couldn't do $file: $!&quot; unless defined $return; warn &quot;couldn't run $file&quot; unless $return; } } </PRE> <HR>