Your question raises some more questions like....

• How big is file1? If the keys fit into memory, a possible solution could be to read all the John1 => "15.T" type keys into a hash and then parse file2 line by line...
• Does the order of entries in the output file play any role?
• May there be multiple matches and how to treat them?
• Do you count the indexes starting with 0 or 1?
• What is the significance of the dot+character (.T) after the index (15)? E.g., do they select a different file2?
• Is this a one-time task? If not, why not start using a database?
• Why not use a database?
• What have you done so far (show some Perl code or describe your approach)?
• Since this is a common question, did you use Super Search? You might find something like Searching Huge files.
• Why shouting at Perl? It is mostly harmless ;-)
• ...

---

---

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! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

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:
	&		&
	<		&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.