<div>
in that case nf is <br />
nf=&quot;tato-matty&quot;
</div>


<div>
In the first statement, you are trying to form a variable name run time and trying to get the value of that variable.<br />
<br />
So<br />
<br />
The value of <br />
<br />
$tato-matty_sw_py_th<br />
<br />
This should be<br />
tato_matty
</div>


In the first statement, you are trying to form a variable name run time and trying to get the value of that variable.

So

The value of

$tato-matty_sw_py_th

This should be
tato_matty

<div>
sorry this is not perl... this is shell scripting 
</div>


sorry this is not perl... this is shell scripting

<div>
Yes, I know. &nbsp;I hope the above answers are making sense.
</div>


Yes, I know.  I hope the above answers are making sense.

<div>
<div class="content wysiwyg-content">
<br />
eval dat=&quot;$&quot;${nf}_sw_py_th<br />
<br />
if [ x$dat != &quot;x&quot; ]<br />
<br />
what is the meaning of above statement in perl ?
</div>
</div>



eval dat="$"${nf}_sw_py_th

if [ x$dat != "x" ]

what is the meaning of above statement in perl ?

perl

Perl is a high-level, general-purpose, interpreted, dynamic programming languages with over 25 years of development. Perl 5 runs on over 100 platforms from portables to mainframes and is suitable for both rapid prototyping and large-scale development projects.  Perl gained widespread popularity as a Common Gateway Interface (CGI) scripting language, in part due to its regular expression and string parsing abilities. In addition to CGI, Perl is used for graphics programming, system administration, network programming, finance, bioinformatics, and other applications.

Perl

The term 'shell' refers to a general class of text-based command interpreters most often associated with the UNIX and Linux operating systems. Popular shells include Bourne, Debian Almquist (dash), Korn (ksh), Bourne Again (bash) and the C shell family (csh). Some view the DOS 'cmd' prompt as a minimal shell of sorts. It is also possible to install Cygwin on Windows and emulate a full Unix environment with complete shell capabilities. Terminal emulators, such as xterm, GNOME Terminal and OS X Terminal, can be used to access shell.

Shell Scripting

A regular expression ("regex") is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. Regular expression processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK. Many programming languages provide regular expression capabilities, some built-in, for example Perl, JavaScript, Ruby, AWK, and Tcl, and others via a standard library, for example .NET languages, Java, Python and C++ (since C++11). Most other languages offer regular expressions via a library.