use strict;  
use warnings;  

my $line = <DATA>;

while(<DATA>) {
    if(/^sb1 1.0 142r$/) {
        print substr($line, 0, -13) . "\n";
    } else {
        print $line;
    }
    $line = $_;
}
print $line;

__DATA__
lines before the changed section
4.62399E+09 2.90871E+09 7.17338E+14
sb1 1.0 142r
lines after the changed section
another instance of the lines to be changed
4.62399E+09 2.90871E+09 7.17338E+14
sb1 1.0 142r
another line with 7.17338E+14 in it
the rest of the file

##</code><code>##

lines before the changed section
4.62399E+09 2.90871E+09
sb1 1.0 142r
lines after the changed section
another instance of the lines to be changed
4.62399E+09 2.90871E+09
sb1 1.0 142r
another line with 7.17338E+14 in it
the rest of the file