If you simply want to strip the NA from the beginning of a string, you can use s/PATTERN/REPLACEMENT/ (see perlop). This will not affect IDs that do not start with NA. For example,

use strict;
use warnings;

for ( 'NA12345', 67890 )
{
    my $id = $_;
    print "$id -> ";
    $id =~ s/^NA//;
    print "$id\n";
}

__END__
NA12345 -> 12345
67890 -> 67890
[download]

Update: I think I misread the question. If you want to allow an optional NA in the line that reads

next unless $line =~ m{^(\S+) (\d+) (.*)};
[download]

then you can change it by using a noncapturing set of parens (see perlre). For example:

use strict;
use warnings;

for( 'string1 NA12345 other stuff',
      'string2 67890 more stuff' )
{
    if( $_ =~ m/^(\S+) ((?:NA)?\d+) (.*)/ )
    {
        print "matched: $2\n";
    }
}

__END__
matched: NA12345
matched: 67890
[download]

Update 2: It looks like your regex is simply capturing 3 fields separated by a single space. If that is the case, split might be more appropriate.

use strict;
use warnings;

for( 'string1 NA12345 other stuff',
      'string2 67890 more stuff' )
{
    my @elements = split( /\s/, $_, 3 );
    print( '[', join( '][', @elements ), "]\n" );
}

__END__
[string1][NA12345][other stuff]
[string2][67890][more stuff]
[download]

HTH

---

---

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.