You could adapt this:

#! perl -slw
use strict;

open I, '<:raw', $ARGV[0] or die $!;
my $regex = $ARGV[1] or die 'No search pattern supplied.';


my $o = 0;
my $buffer;

## Read into the buffer after any residual copied from the last chunk
while( my $read = read I, $buffer, 4096, pos( $buffer )||0 ) {

    while( $buffer =~ m[$regex]gc ) {

        ## Print the offset, the matched text plus (following) context
        print $o + $-[0], ':', substr $buffer, $-[0], 100;
    }

    ## Slide the unsearched remainer to the front of the buffer.
    substr( $buffer, 0, pos( $buffer ) ) = substr $buffer, pos( $buffe
+r );

    $o += $read; ## track the overall offset.
}

close I;
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