How about the following? The variable $text should contain the text you want to check.

if(
 $text =~ 
  m{ 
     (         #open capturing parenthesis
         \d+   #numbers before the period
         \.    #literal period
         \d+   #numbers after period
     )         #closing capturing parenthesis
     \s*       #optional spaces
     °     #degree symbol
     F         #literal letter F
  }xms){
     my $temp = $1;   # '$1' is what was found in capturing ()
     if($temp > 75){
         #code to send message
     }
}else{
    #code to deal with not finding temperature data.
}
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or without comments

if( $text =~ m{ (\d+ \. \d+) \s* ° F }xms){
     my $temp = $1;
     if($temp > 75){
         #code to send message
     }
}else{
    #code to deal with not finding temperature data.
}
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Note: Updated several times