The easiest solution is probably Tie::File. It's been a standard part of the Perl distribution for a few years.

Super Search is your friend. A search SoPW only for "File line" and root nodes only finds (among many others):

• Processing text file in reverse-order linewise
• how can i read only the last line of a files
• updating/modifying line in a file
• moving the filehandle to anyline of a file
• Reading Lines from Text file

i want to read just the second line from a file and replace it other. Basically updating the file if needed. i am replacing using 'sed'. But i need to check the condition whether there is a need to update.for that i need to read the 2nd line frm the file...how do i do it????

This is a faq: see perldoc -q 'change one line'. It points you to Tie::File which others already suggested you. But if the files to modify are not that large you may adopt an ad hoc solution, e.g.

$ cat foo.txt
foor
barr
bazz
quux
$ perl -lpi.bak -e 's/bar/rab/ if $.==2' foo.txt
$ cat foo.txt
foor
rabr
bazz
quux
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Without knowing more details about your actual needs it's hard to say...