=over

=item HANDLE->input_line_number( EXPR )

=item $INPUT_LINE_NUMBER

=item $NR

=item $.
X<$.> X<$NR> X<$INPUT_LINE_NUMBER> X<line number>

Current line number for the last filehandle accessed.

Each filehandle in Perl counts the number of lines that have been read
from it.  (Depending on the value of C<$/>, Perl's idea of what
constitutes a line may not match yours.)  When a line is read from a
filehandle (via C<readline()> or C<< <> >>), or when C<tell()> or
C<seek()> is called on it, C<$.> becomes an alias to the line counter
for that filehandle.

You can adjust the counter by assigning to C<$.>, but this will not
actually move the seek pointer.  I<Localizing C<$.> will not localize
the filehandle's line count>.  Instead, it will localize perl's notion
of which filehandle C<$.> is currently aliased to.

C<$.> is reset when the filehandle is closed, but B<not> when an open
filehandle is reopened without an intervening C<close()>.  For more
details, see L<perlop/"IE<sol>O Operators">.  Because C<< <> >> never does
an explicit close, line numbers increase across C<ARGV> files (but see
examples in L<perlfunc/eof>).

You can also use C<< HANDLE->input_line_number(EXPR) >> to access the
line counter for a given filehandle without having to worry about
which handle you last accessed.

Mnemonic: many programs use "." to mean the current line number.

=back