Not a regex, but this seems to do the job ... 
my $str =
  "25 {fred and barney} text 2.36 12.0 {bam bam} text {pebbles}";

print "before - $str\n";

substr($str, pos($str) - length($1), length $1) =~ s/ /_/g
  while $str =~ /\G .*? { ( [^}]+ ) } /xg;

print "after  - $str\n";

__output__

before - 25 {fred and barney} text 2.36 12.0 {bam bam} text {pebbles}
after  - 25 {fred_and_barney} text 2.36 12.0 {bam_bam} text {pebbles}

[download]
Substituting bracket contents with a variable is somewhat simpler 
my $str =
  "25 {fred and barney} text 2.36 12.0 {bam bam} text {pebbles}";

print "before - $str\n";

$str =~ s/{ ([^}]+) }/{$rep}/xg;

print "after  - $str\n";

__output__

before - 25 {fred and barney} text 2.36 12.0 {bam bam} text {pebbles}
after  - 25 {between brackets} text 2.36 12.0 {between brackets} text 
+{between brackets}

[download]
See. perlre for more info on regular expressions in perl.
HTH

_________
broquaint

In reply to Re: looking for a regex by broquaint
in thread looking for a regex by Anonymous Monk

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