Let's have a look at what code you have got so far!

If you only want text after the matching line, then the easiest approach is probably to set a 'flag' on successful matching :

use strict;
use warnings;

## flag
my $flag = 0;

while(<DATA>){
  my $line = $_;
  if ($flag){
    ## we have already seen the flag, so print the line
    print $line;
  }
  else {
    ## haven't yet seen the flag
    ## so let's see if this line contains it
    
    if ($line =~ m/^Sentence/){
      ## if we do see it, set the flag, 
      ## so we no longer look for it, but just spew out the lines
      $flag = 1;
    }
  }
}
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