Your code does appear to do what you are asking for so I find your question a bit confusing. However some simplifications are possible to make things more clear.

You have 2 ways to exit the loop:

- until ("" ne $gotit)
- if($gotit){last;}

[download]
I would simplify to one condition. Note null string is "false". Also $gotit doesn't appear to be necessary because it appears that the lookfor() method is looking for what you told it to with the are_match() method. 
$PortObj->are_match("abcd"); # Pattern to match
send_prompt();  #I presume this happens?

while (!$PortObj->lookfor()  )
{
   print("Pattern is not detected\n");
   send_prompt();  #re-prompt
}

# pattern is detected here ... we continue

[download]
unless and until can sometimes confuse folks, so I tend to prefer using "while" for the vast majority of my loops like this.

In reply to Re: pattern detection inside until loop in perl by Marshall
in thread pattern detection inside until loop in perl by vrushali

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.