How to insert a line into the middle of an existing file

Question

consider an example where i want to insert few lines of text when particular patter matches(if $line=~m/few lines in here/ then insert lines in next line):

*current file:*

"This is my file and i wanna insert few lines in here  and other
text of the file will continue."

*After insertion:*

"This is my file and i wanna insert few lines in here  this is my
new text which i wanted to insert and other text of the file will
continue."

This is my code:

my $sourcename = $ARGV[1];
my $destname = $ARGV[0];
print $sourcename,"\n";
print $destname,"\n";
my $source_excel = new Spreadsheet::ParseExcel;  
my $source_book = $source_excel->Parse($sourcename) or die "Could not open source Excel file $sourcename: $!";

my $source_cell;
#Sheet 1 - source sheet page having testnumber and worksheet number
my $source_sheet = $source_book->{Worksheet}[0];            #It is used to access worksheet

$source_cell = $source_sheet->{Cells}[1][0];                #Reads content of the cell;
my $seleniumHost = $source_cell->Value; 
print $seleniumHost,"\n";

open (F, '+>>',"$destname") or die "Couldn't open `$destname': $!";
my $line;

while ($line = <F>){
print $line;
if($line=~m/FTP/){
#next if /FTP/;
print $line;
print F $seleniumHost;}

Answer 1

The perlfaq covers this. How do I change, delete, or insert a line in a file, or append to the beginning of a file?

Files are fixed blocks of data. They behave much like a piece of paper. How do you insert a line into the middle of a piece of paper? You can't, not unless you left space. You must recopy the whole thing, inserting your line into the new copy.

Answer 2

In a perl one-liner :

perl -ane 's/few lines in here  and other\n/this is my\nnew text which i wanted to insert and other /; s/continue./\ncontinue./; print ' FILE

If you don't want a one-liner, it's easy to takes the substitutions in any script ;)