I suspect any one-liner is going to be somewhat unwieldy. Here's one using Tie::File: 

ken@ganymede: ~/tmp
$ cat > pm_add_header_1
HEADER
XXXXX
YYYYY
ZZZZZ
ken@ganymede: ~/tmp
$ cat > pm_add_header_2
AAAAA
BBBBB
CCCCC
DDDDD
ken@ganymede: ~/tmp
$ perl -Mstrict -Mwarnings -MTie::File -e 'my @f; my $i = 0; tie @{$f[
+$i++]}, q{Tie::File}, $_ or die $! for @ARGV; unshift @{$f[1]}, $f[0]
+[0];' pm_add_header_1 pm_add_header_2
ken@ganymede: ~/tmp
$ cat pm_add_header_2
HEADER
AAAAA
BBBBB
CCCCC
DDDDD
ken@ganymede: ~/tmp
$

[download]

-- Ken

In reply to Re: Single line insert to the start of a file by kcott
in thread Single line insert to the start of a file by darklord_999

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.